We will continued our studies of a library of monoclonal antibodies to rat mammary gland, determining their specificity for cells of the mammary gland, or other organs of the rat, and of tumours induced in the mammary gland by NMU. We will study selected antibodies to see whether they inhibit growth of mammary cells in culture, development of the gland in young rats, tumour incidence after NMU injection, and whether they cen cause the regression of already existing tumours. We will study the relation between epithelium and mesenchyme in the development of the rat or mouse mammary gland using cultures of epithelial and mesenchyme cells as well as organ cultures. We will investigate further the nature of fusiform cells that arise in cultures of epithelial rat mammary cells as well as in lung metastases of mouse mammry tumours. We will investigate the formation of alveoli in organ cultures of mouse mammary glands and the origin of myoepithelial cells in mouse mammary tumours using chymeras in organ culture or allophenic mice. We will whether rat tumors produce growth factors for epithelial or mesenchyme cells. We will investigate the behavior of oncogenes demonstrable in rat or mouse mammary tumours during tumour progression. We will try to improve the methodology for making human monoclonal antibodies to human breast cancer cells, and to make hybridomas using lymphocytes of breast cancer diagnosis or treatment.